Luciano Vietto is storming here in that position. 27 goals in 25. Ronaldo 29 in 28 as the left striker, he's old now, but he's Ronaldo. Right striker Bale has 16 in 14 and a couple of regens have scored 1 per game as well when Bale is injured.
Everyone I've put there has 1+ goal per game so far. Pretty sure any good striker will do, but if you want the same class as Falcao in the first couple of seasons you might have to go Lewandowski/Agüero/Ronaldo/Messi/etc. I've gotten Ronaldo to Man Utd in several saves in the 2nd season, so it's not impossible. You get stupid amounts of money to spend if you're successful at Man Utd.
If you don't wanna spend record sums, and don't mind players that aren't at their full potential that early, I'd try to grab one of Icardi, Dybala, Vietto, Berardi, Malcom, Calleri. They've all been huge successes for me in different Man Utd saves.
In my current save I haven't been at Man Utd (yet), but I see they got Harry Kane for £28,5M and he's one of the highest rated strikers in the game in this save and looks a beast. I've no idea if he's "random" though, maybe he was just buffed a lot in the latest patch because of his performance this season.